Group Project: Dividing Head - Organization and Design

Shotgun

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A thread discussing the actual build is included below. This thread has been dedicated to the design and organizational phase of the project. Read this thread to understand what we are discussing in the follow on thread here:



This is a follow on thread to the one started by GunOfNavarone.

Join this thread if you would like to join in on the construction of a dividing head.

One of the HM members, Mark_f, shared the process of building his dividing head. Please read the thread so that we're all have a basic understanding of what will be involved, what the end product will look like, and share a common nomenclature.

To begin with, I already have a 40:1 worm gear, and the material and tooling to make several more from 7071 alloy aluminum. This piece is 1.000" inch thick, 3.185" diameter.

The worm is a piece of 1" acme rod that is 1" long. I drilled and tapped the set I have for a 3/8 bolt, but that can be modified. I have material for 9 more pieces.

My shaft is 1.5" CRS, 4.5" long, threaded at 8tpi. I have the material for 2 more pieces. Mark_f bored his out for 3C collets. I have MT3 on my lathe and mill. Would this feature be best left to the final owner?

I'd like to start with Mark_f's design but improve/simplify it with hindsight. For instance:

- the trunnion cap and disk mount arm can be one piece?
- the trunnion can be shortened to eliminate the need for the base extension?
- a pin can be incorporated into the second support to allow the trunnion to be locked into multiple positions?
- the worm can be internal threaded to eliminate the need for the nut on the crank arm?
 

Attachments

  • DH AY001 DividingHead.step
    19.1 MB · Views: 32
  • Dividing Head BOM.pdf
    12.9 KB · Views: 18
  • Dividing Head BOM.xls
    34 KB · Views: 7
  • Dividing Head Drawings.pdf
    2.1 MB · Views: 42
Last edited:
I'm barely competent at it, but I can do a 3D drawing. I have SolidWorks. This would definitely be a job that someone who knows drafting would do a better job at, though.
 
I have MT3 on my lathe and mill. Would this feature be best left to the final owner?
my lathe has a 5c spindle it is a common size and I could pick it up with my "new" tenths indicator and bore it out but the ways are worn so it wont be too accurate
 
As a starting point for discussion, I'm making an initial division of the work/parts:

1) Drawing (Ernest, but would prefer someone more qualified)
2) Worm, Gear, and Spindle Shaft (Ernest)
3) Trunnion and Bearing with End Plates
4) Base
5) Crank with Sector Arms, Index Plates
6) Chuck/Front Index/Backing Plate, Spindle Lock with Indexing Pin

Some volunteers will have material or tools on hand that would change the design or work division. Everything is up for compromise. But, is it looking like a 5 person group is about right?
 
my lathe has a 5c spindle it is a common size and I could pick it up with my "new" tenths indicator and bore it out but the ways are worn so it wont be too accurate
The shaft for 5C collets is 1.25". With the 1.5" stock I have, that will leave a .125 wall thickness on the spindle before it starts the taper. Even less if there is to be any clearance for the drawbar. Once the taper and then the threads for a backing plate are added, will there be anything left?

Should the shaft nose be left as an exercise for each member to adapt to their unique situation?
 
I don't think 5c would fit with the thread on the OD. 3c would likely be fine, or just leave it up to the members.
 
I don't think 5c would fit with the thread on the OD. 3c would likely be fine, or just leave it up to the members.
So that begs the question of whether the spindle should be threaded at all. If left raw, how would the front indexing plate (or, should we call it the Quick Indexing Plate) be attached?

I'm starting to think that the 1.5" CRS that I made the spindle I have from is not appropriate for this project. While I could drill it for a roll pin to indicate the rotary position of a Quick Indexing Plate, there would be no shoulder for it to indicate against. If I switched to a 2" round, then I could make it match the spindle on my Atlas, including the MT3 taper on the inside. That would give me the flexibility to use all my tooling, since my mill is also MT3. For other members, I'd leave it raw to do that part as they see fit, but there still wouldn't be room for a 5C draw bar would there?
 
threaded would be a good idea if we have a chuck that stays with it.
 
In a perfect design, the gear and the worm would be brass? Mark's base proved to be inadequate and he added a support. The base should be redesigned. Do you think a horizontal/vertical rotary table would be an easier project?
Robert
 
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